The present work concerns the study of the phase transition of plattnerite [β-PbO₂ lead (IV) oxide]-based samples when they are analysed by Raman spectroscopy. The laser-induced degradation process was carried out either on historical painting samples, where plattnerite was present as a degradation product of lead-based pigments, or commercial plattnerite samples as powder and pellets. The Raman spectra of plattnerite taken at low excitation power, to avoid phase transformations, are reported up to low wavenumbers, and they were characterized by the features at 159, 380, 515 and 653 cm⁻¹ and a shoulder at 540 cm⁻¹. The degradation of plattnerite was induced by increasing the laser power on the sample, and the formation of its secondary products red lead (Pb₃O₄), litharge (α-PbO) and massicot (β-PbO), when varying the laser power, is discussed. The analyses were performed in a controlled condition by coupling the Raman spectrometer to a temperature-controlled stage (Linkam THMS600- Renishaw), which allows for varying the sample temperature (from room temperature up to 600 °C) and keeping it constant inside the stage during the analysis. In this way, commercial plattnerite samples were heated by increasing the cell temperature to verify the temperature range at which the phase transitions of lead dioxide occur. In addition, thanks to the construction of temperature ramps, all the degradation pathways were shown, and other lead compounds were identified, generated by the laser power contribution. A different behaviour was found between pigments from historical painting samples and commercial samples under the effect of the laser. This information could be useful in order to recognize their nature when they are found in cultural heritage materials.

中文翻译：

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使用温度控制的共聚焦拉曼显微镜研究二氧化铅（白铅矿）的相变

本工作的担忧plattnerite的相转变[β-PBO的研究₂铅（IV）氧化物]为基础的样品时，他们通过拉曼光谱法进行分析。激光诱导的降解过程是在历史绘画样品上进行的，在该历史绘画样品中，白铅矿是以铅基颜料的降解产物形式存在的，或者是商业性的白铅矿样品以粉末和颗粒的形式进行的。据报道，为了避免相变，在低激发功率下获得的白铁矿拉曼光谱高达低波数，其特征在于159、380、515和653 cm ^{-1处的特征}以及540 cm ^-1处的肩部。通过增加样品上的激光功率和其次要产物红铅（Pb₃ Ò ₄），讨论了改变激光功率时的石渣（α-PbO）和Massicot（β-PbO）。通过将拉曼光谱仪与温度控制平台（Linkam THMS600- Renishaw）耦合，在受控条件下进行分析，从而可以改变样品温度（从室温到600°C）并在平台内保持恒定在分析过程中。通过这种方式，通过增加样品池温度来加热商用铂金矿样品，以验证二氧化铅发生相变的温度范围。此外，由于温度斜坡的构造，显示了所有降解途径，并鉴定了由激光功率贡献产生的其他铅化合物。在激光的作用下，在历史绘画样品和商业样品的颜料之间发现了不同的行为。当在文化遗产资料中发现它们的性质时，此信息可能很有用。